Control for container filling machine

ABSTRACT

A control circuit for filling apparatus of the kind wherein there is a nozzle through which liquid is delivered to a container and a filling valve for controlling flow through the nozzle. The circuit includes valve means that supplies sensing pressure to a sensing tube, an exhaust valve through which the pressure in the circuit is adapted to be exhausted to below operating pressure to terminate the filling operation by closing the filling valve in the nozzle and a diaphragm responsive to back pressure developed in the sensing tube to effect operation of the exhaust valve. There is also in the circuit, valve means for at times terminating the flow of sensing air and injecting high-pressure air into the sensing tube to clear it.

United States Patent 91 [111 3,783,913

Trusselle Jan. 8, 1974 CONTROL FOR CONTAINER FILLING Primary Examinerl-loust0n S. Bell, Jr.

MACHINE Assistant ExaminerFrederick R. Schmidt 75 Inventor: William H. Trusselle, Braintree,

Mass.

[73] Assignee: Pneumatic Scale Corporation, [57] ABSTRACT Qu y MaSS- I A control circuit for filling apparatus of the kind [22] Filed: July 8 1971 wherein there is a nozzle through which liquid is deliv- Appl. No.: 160,840

U.S. Cl 141/46, 141/91, l4l/l98 Int. Cl 1365b 31/00, B65b 57/l4 References Cited UNITED STATES PATENTS 8/1970 Allen l4l/9O Vergobbi l4l/l98 ered to a container and a filling valve for controlling flow through the nozzle. The circuit includes valve means that supplies sensing pressure to a sensing tube, an exhaust valve through which the pressure in the circuit is adapted to be exhausted to below operating pressure to terminate the filling operation by closing the filling valve in the nozzle and a diaphragm responsive to back pressure developed in the sensing tube to effect operation of the exhaust valve. There is also in the circuit, valve means for at times terminating the flow of sensing air and injecting high-pressure air into the sensing tube to clear it.

15 Claims, 6 Drawing Figures PAIENIEDJMI 819M 3783.913

SHEET 1 [IF 5 ATTORNEY PAIENTEB M 81974 SHEET 2 OF 5 PMENIEDJAN 81914 3.788.918

SHEET U (1F 5 //VVE/VTOR W/'///'am H. Trussel/e zi giidzzm w ATTORNEY CONTROL FOR CONTAINER FILLING MACHINE BACKGROUND OF THE INVENTION Apparatus of the foregoing kind is shown in my U.S. Pat. No. 3,580,298 and the Vergobbi U.S. Pat. Nos. 3,182,691 and 3,207,189. This invention is concerned with improvements in apparatus of the foregoing kind designed to prevent impairment of the control circuit by the happenstance of the high-pressure air, which is employed to effect clearing of the sensing tube, gaining access to the sensing diaphragm and causing injury thereto, or the liquid in the container being filled backing up into the sensing tube and clogging the relatively small air passages therein and to the further improvements of providing for more sensitive response and accuracy of adjustment of the sensing diaphragm and the exhaust valve and for preventing unauthorized tampering with the adjustment of the latter valve.

SUMMARY OF INVENTION in the filling apparatus shown in my patent there is a control circuit to which air pressure is supplied including means operable by the pressure to initiate a filling operation, a sensing tube through which low pressure sensing air is adapted to flow into the top of the container and a sensing diaphragm displaceable by back pressure developed in the sensing tube when the liquid rises in the container to the end of the tube. The circuit includes a pressure chamber to which the circuit pressure is supplied and from which pressure is allowed to bleed through a nozzle at a predetermined rate such as to maintain lower than normal circuit pressure therein. An exhaust diaphragm is connected with the pressure chamber and is operable by an increase in pressure in the chamber to open an exhaust valve in the circuit to exhaust air therefrom and thereby stop the filling operation. The pressure in the pressure chamber is increased by movement of the sensing diaphragm toward the aforesaid nozzle. The circuit also includes conductor means for supplying low-pressure sensing air, conductor means for supplying a higher pressure blowdown air for clearing the sensing tube and valve means operable to control the supply of sensing air to the sensing tube and at times to disconnect the sensing air from the sensing tube and connect the higher pressure, blowdown air thereto. In accordance with this invention to prevent back flow of the higher pressure, blow-down air into the low pressure conductor which may cause injury to the sensing diaphragm, the valve means employed herein comprises normally open and normally closed valve parts adapted to be displaced by air pressure; said valve parts respectively connecting the low pressure conductor to the valve means and a high pressure conductor to the valve means, means operable to connect both of said valve parts to the operating pressure in the circuit and means for differentially resisting displacement of the valve parts so that displacement of the normally open valve part precedes displacement of the normally closed valve part. In accordance with another aspect of the invention the circuit also includes means for preventing back flow of liquid from the con tainer being filled, in the event of blockage, through the sensing tube into the valve means, comprising a check valve situated between the sensing tube and the valve means. As constructed the check valve comprises a light-weight disk supported within a chamber interposed in a conductor between the sensing tube and the valve means, said chamber having vertically spaced upper and lower ports at its opposite ends of smaller diameter than the disk. The port at the lower end is provided with radial slots longer than the radius of the disk and under normal conditions the sensing air flowing through the valve holds the disk against this lower port flowing through the radial slots about the disk. Liquid backing upwardly into the sensing tube will lift the disk against the vupper port closing it. A further improvement in the circuit shown herein comprises supporting the sensing diaphragm at its edge in a horizontal position with one side exposed to the sensing air so that the back pressure developed in the sensing tube displaces the diaphragm downwardly. The nozzle through which the pressure from the pressure chamber escapes is supported in a perpendicular position opposite the center of the sensing diaphragm, and a coil spring supported between the diaphragm and an adjustable part on the venting nozzle holds the diaphragm in an inoperable position so long as there is no back pressure, and the adjustable part provides for adjusting the resistance of the spring to compression and thereby, displacement of the sensing diaphragm to the back pressure. Supporting the diaphragm in a horizontal rather than a vertical position provides for greater sensitivity, uniformity of response and adjustment for a predetermined back pres- 1 sure. The exhaust valve in accordance with this invention, to provide for greater sensitivityand more direct action, is supported by spaced diaphragms for rectilinear movement perpendicular thereto relative to the exhaust port and operation of the exhaust valve is effected by a connection from the pressure chamber which transmits the pressure in the chamber to the confronting surfaces of the diaphragms. A spring normally holds the exhaust valve in its closed position and the diaphragm which is more remote from the exahust port is of larger effective area than the other of the two so that an increase in pressure in the pressure chamber moves the exhaust valve away from the port. A threaded part engaged with the spring and containing at one end a recess for receiving an adjusting tool is provided for adjusting the resistance of the spring to displacement, whereby the pressure which will open the exahust valve can be predetermined.

The invention will now be described in greater detail with reference to the accompanying drawings wherein:

FIG. 1 is a view of the improved control unit with the upper part in section and the lower part in elevation;

FIG. 2 is a view at the lower part of the unit in section;

FIG. 3 is an enlarged section at the lower left-hand corner of the unit shown in FIG. 2;

FIG. 4 is a diametrical section taken in the plane of the paper of a check valve connecting the lower part of the unit to the sensing tube shown in elevation in FIG. 1-

FIG. 5 is a section taken of the line 5-5 of FIG. 4;

and

FIG. 6 diagragrammatically illustrates the operation of the control circuit.

Referring to the drawings this invention relates to an improved control unit for the container filling machine heads supported thereabove for filling. Following filling the containers are discharged from the paltforms. There is a control unit associated with each head and each control unit 10, as shown in FIG. 1, is supplied from a common source with high-pressure air for effect'ing operation of the apparatus through a conductor 12, such pressure being employed to effect opening and closing of a material filling valve situated in the filling head which controls the flow of the material with which the containers are to be filled; with low-pressure air, for sensing, through a conductor 14; and with variable pressure air, for blowdown depending upon the product being processed, through a conductor 16. Each unit comprises a valve block 18 into the bottom side of which is threaded (FIGS. 1 and 2), the upper end of a cylinder 20 containing a piston not shown from which extends a piston rod 22 (FIG. 6), the piston rod being adapted as shown in the aforesaid patent by downward displacement to open the material filling valve in the filling head. The block 18 has also, at its lower side, an adapter 24 (FIG. 1) through which the sensing air is supplied by way of a conductor 26, a check valve 28 and a conductor 30 to the upper end of a sensing tube 34 which is disposed to enter the open top of the container with-the filling nozzle through which the material is introduced into the container, and may be disposed within the nozzle or in parallel relation thereto. The block 18 is provided at its right-hand side with two trips 33 and 35 (FIG. 2), respectively. The trip 33 is operable to initiate a filling operation and the trip 35 is operable to initiate blowdown to clear the sensing tube.

Referring to FIG. 2, which more specifically illustrates the internal structure of the valve block 18, there is at the upper left-hand side of the block a pilot valve unit 36 comprising a middle or intermediate chamber 38 and end chambers 40 and 42 at the opposite ends thereof, formed in a core piece 44 recessed into the block 18 and a valve element 46 supported in the chambers. At the ends of the intermediate chamber 38 there are valve seats. The valve element 46 has heads 48 and 50 situated in the end chambers and a stem 52 connecting them which extends through the intermediate chamber and is supported for longitudinal movement for, on the one hand, to engage valve head 48 with its seat and disengage the valve head 50 from its seat, and on the other hand disengage the valve head 48 from its seat and engage the valve head 50 with its seat. Such longitudinal movement is provided for by flexible diaphragms 53 and 55 to which the heads are secured and by means which the valve element is mounted at its ends in the end chambers. The end chamber 40, at the outer side of the diaphragm 53, is in communication with a high pressure line 56 in the valve block which, in turn, is connected with a chamber 58 to which high pressure air is supplied by way of the conductor 12 shown in FIGS. 1 and 2. The end of the chamber 42, at the outer side of the diaphragm 55, is in communication with a pilot passage 60 by way of a normally closed two-way trip valve 61, operation of which is effected by the trip 33. Between the valve seats there are radial ports 62 in communication at one end with the intermediate chamber 38 and at their other ends with an annual passage 64 formed in the core piece 44. The annual passage 64 is, in turn, in communication with passages 66 and 68, the latter entering the top of the cylinder 20. The diaphragm 53 contains ports 70 through which the pressure fluid from the high pressure passage is free to flow from the end chamber 40 into the intermediate chamber 38 when the valve head 48 is disengaged from its seat and the stem 52 has an axial passage 72 which extends from midway between opposite ends of the stem through the valve head 50, which allows communication between the intermediate chamber 38 and the end chamber 42 in both the engaged and disengaged positions of the valve head 50. The portion of the end chamber 42, inwardly of the diaphragm 55, contains an axial opening 74, which is in communication with an annular passage 76 formed in the core and this in turn is in communication with an exhaust passage 78 open to the atmosphere. Actuation of the trip valve 61, which is connected to the chamber 58 by a passage 80, will supply a pulse of high pressure air through the pilot passage 60 to the outer side of the diaphragm 55 so as to displace the valve element 46 in a direction to move the valve head 50 into engagement with its seat and move the valve head 48 away from its seat whereupon high pressure air from passage 56 enters into the intermediate chamber 38, and passing through the axial passage 72 to the outer side of the diaphragm 55, holds the valve element displaced to the right. The high pressure air supplied to the intermediate chamber 38 flows through passages 66 and 68 to the upper end of the cylinder 20 to lower the piston rod therein and effect filling by opening the filling valve. The valve element 46 will remain open in filling position as long as the pressure in the system remains at its operating level.

During the filling operation, low pressure sensing air from the conductor 14 enters an annular passage 84 in a valve unit 88 at the lower left side of the valve block, similar to the valve unit 36. The unit 88 embodies an intermediate chamber 94 and end chambers 95 and 97. A valve element 92, having at its ends valve heads 91 and 93, is supported in the chambers by diaphragms 96 and 101. The entering low pressure air passes through a connecting passage 99 into the intermediate chamber 94 by the valve head 91, which is normally held away from its seat by a spring 87 at the right end of the valve element, and from thence through radial passages 103 into a connecting annular passage 105. A passageway 102 connects the passage 105 with the adapter 24 so that low pressure air is supplied through the conductors 26, check valve 28 and conductor 30 to the upper end of the sensing tube 34 (FIG. 1). The low pressure sensing air is delivered continuously through a passage 108 to the valve unit 88, which normally remains open during the filling operation except at such times, and by such means as will be described for supplying a blowdown pressure to the sensing tube 34 to clear its open end of any accumulation of the material supplied to the container. To initiate blow-down, a normally closed trip valve 107 is provided which is operable by the trip 35 to supply pressure through a passage 104 to the outer side of the diaphragm 96 of the valve unit 88. Pressure supplied to the outer side of the diaphragm 96 will shift valve element to a position such as to move the valve head 91 into engagement with its seat and disengage the valve head 93 from its seat thereby cutting off communication between the intermediate chamber 94 and the passage 84 through which the sensing air is normally supplied.

In the control circuit shown in the aforesaid patent, the sensing diaphragm is supported in a vertical position and is without adjustment and the exhaust diaphragm operates indirectly in effecting opening of the exhaust valve. As herein illustrated, the sensing diaphragm is supported in a horizontal position and provided with means for adjusting its response to the sensing pressure to thereby improve its sensitivity and provide for response to different back pressures and the exhaust diaphragm is mounted for direct actuation of the exhaust valve to insure faster and more sensitive operation. Also, in accordance with the improvement herein disclosed, the adjustment for the'exhaust diaphragm is designed to discourage unauthorized tampermg.

To accomplish the foregoing, the passage 108 through which the low pressure sensing air is delivered to the valve unit 88 is connected by way of a passage 110 to the upper end of a chamber 112 formed in a block 114- at the top of the valve block 18. A roll type diaphragm 116 is mounted in the chamber in the upper end and is secured therein at its edge 118 in a horizontal position with a space between it and the upper end of the chamber. A valve element 120 is mounted atthe center of the diaphragm with a portion extending downwardly therefrom. A nozzle 122 is mounted in the chamber at the lower end with a portion comprising a nozzle tip 126 extending upwardly therefrom toward the valve element 120. The nozzle contains a passage 122a which is in communication with a pressure chamber 124 in the block 114. A collar 127 is threaded onto the stem of the nozzle 122 and a coiled spring 128 is mounted about the nozzle between the diaphragm 116 and the collar 127. The spring operates to hold the valve element 120 away from the tip end 126 of the nozzle in a position such that a boss 130 at the upper side of the diaphragm abuts the upper end of the chamber. A grove 132 is provided across the boss so that the sensing air at all times has access to the chamber 112 at the upper side of the diaphragm. Under normal operating conditions during filling, the sensing air is ineffective; however, when the container is filled to an extent to close the sensing tube, a back pressure is developed -in the sensing tube and is communicated through the passage 110 to the upper side of the diaphragm 116 to displace it downwardly toward the tip end 126 of the nozzle.

By turning the collar 127, the resistance of the diaphragm to displacement may be adjusted to respond to a predetermined back pressure in the sensing tube.

The pressure chamber 124 with which the nozzle 122 is in communication is connected to the high pressure air from the passage 56 through a passage 131 containing a restrictor 133. Under normal conditions the pressure in the pressure chamber 121 vents through the tip 126 of the nozzle 122 to the atmosphere. The nozzle opening is of a size such as to maintain the pressure in the pressure chamber 124 at a predetermined lower pressure than that of the source pressure. The pressure chamber 124 is connected by a passage 136 with a chamber 138 in which there is supported an exhaust valve element 140. The support for the exhaust valve element 140 comprises a sleeve 1142, supported at its opposite ends by diaphragms 14 1 and 146 so that it is movable axially with respect to the end of a nozzle 148 providing an exhaust vent in the pressure system which is connected by a passage 150 to the high-pressure passage 56. A housing block 155 is mounted on the block 114 above the upper end of the valve element 140 in which there is a chamber 157. The valve element 140 is normally held against the end of the nozzle 148 so as to maintain an operating pressure in the circuit by coiled spring 151 disposed in the chamber 157 between the upper end of the valve element and an adjustable part 152 supported by a threaded stem 153 extending through the upper end of the chamber. A lock nut 154 provides for supporting the part 152 in a predetermined position of adjustment. With this arrangement displacement of sensing diaphragm 116 by back pressure in the sensing tube decreases the flow of air through the nozzle 122 thereby increasing the pressure in the pressure chamber 124 and comparably the pressure in the chamber 138. The upper one of the diaphragms Mtiis of larger effective area than the lower diaphragm 144 so that the increase in pressure in the chamber 124 displaces the exhaust valve element away from the nozzle 1413 thereby exhausting the pressure in the circuit and such exhaust results in the valve unit 36 shifting to engage the head 18 with its seat and disengaging the head 50 from its seat, thus cutting off the flow of high-pressure air to the cylinder 21) thereby terminating the filling operation.

As thus constructed if by chance a valve unit 88 were to be only partially tripped, as for example, if it were to be partially engaged by its operating cam, insufficient pressure would be supplied to the valve unit 83 to entirely engage the head 51 with its seat, and so the blow-down pressure entering through the disengaged head 93 could pass through the intermediate chamber 94 and into the sensing passage 10$ and from thence into the chamber 112 above the diaphragm 116. This blast of high-pressure air can damage the diaphragm 116 and by causing rapid vibrations of the valve element 120 against the end of the nozzle can damage the tip end of the nozzle.

It is a desirable improvement of this invention to eliminate this problem. Prevention of the bacltflow of the blow-down pressure is accomplished herein by provision of a valve assembly (F168. 1, 2 and 33) supported at the left side of the block 18 over the end of the valve unit 88. The valve assembly 1311 comprises a block 182 bolted over the cavity in which the valve unit 83 is situated containing a central passage 183 in communications with the chamber 97 at the left-hand side of the diaphragm 6 which supports the valve head 91. The block 182 contains a recess 188; concentric with passage 183 in which there is seated one end of a cylinder 190 containing a chamber 192. The end of the cylinder 190 seated in the block 1&2 has an opening 196 concentric with the passage 183. The other end of the cylinder has an internally threaded portion 198 in which there is screwed a plug 21111 which, in turn, is threaded at one end for engagement with the threaded portion 198, and at the other end, has an internally threaded portion 202. Within the chamber 192 there is mounted a piston 204 from which extends axially a piston rod 206, the distal end of which extends through a central opening 208 in the plug 2110. A coil spring 211) is mounted on the piston rod with one end bearing against the plug and the other end against the piston and operates to hold the piston at the right-hand end of the chamber 192. The plug 21111 has fitted into it a three-way valve part 212, one end of which is threaded at 214 for engagement with the threaded portion 202 of the plug, and the other end of which is threaded at 216 to receive an internally threaded coupling member 218 at the end of the conductor 16. The valve part 212 is axially bored to different diameters and has at one end an actuator element 222, which extends from that end along the valve part to a position adjacent a ball 224, which is held against an annular seat 226 by a spring 228, one end of which engages the ball and the other end of which rests against a shoulder 229. The actuator element 222 is normally held away from the ball by a spring 230, one end of which engages a shoulder 231 within the valve part and the other end of which engages a shoulder 233 on the actuator element. At the one end of the actuator there is a head 232, which is adapted by engagement of the piston rod 206 therewith to effect movement of the actuator into engagement with the ball 224 thereby to unseat the ball 224. At the right-hand side of the ball 224, there is a threaded opening 234 into which there is screwed one end of a conductor 236. This conductor is connected by way of a passage within the block 18, an end of which is shown at 239 (FIG. 2), to the'chamber 95 at the right-hand side of the diaphragm 101 supporting the valve head 93. Thus, when the ball 224 is unseated the blowdown pressure from the conductor 16 will be permitted to pass through the valve seat 226 and through the conductor 236 to the right side of the chamber 95. To insure seating of the valve head 91 before the valve head 93 is unseated, the spring 87 which holds the valve element in its open, that is, sensing position with the head 91 disengaged from its seat and the head 93 engaged with its seat, is selected to be less resistant to displacement than the spring 230 in thevalve assembly 180. As a consequence, when a pulse of high-pressure air is delivered to chamber 97 between the left side of the diaphragm 96 supporting the valve head 91 and the piston 204, the valve element 92 will be shifted to the right to engage head 91 with its seat thereby blocking communication between the intermediate chamber 94 and the passage 99 before the ball 224 is disengaged from its seat so that it is impossible for the blowdown pressure to enter the sensing passage 108 which leads to the diaphragm 116.

in the control circuit of the aforesaid patent it has happened that pressure was developed in the container during the filling operation by reason of an obstruction at the mouth of the container causing the liquid in the container to rise through the sensing tube into the passages in the valve block 18 thusobstructing them.

Disassembly of the valve block for cleaning and reassembling disables the apparatus for a considerable length of time and, hence, such a happenstance' is to be avoided. To remedy this possibility there is, as shown in FIGS. 1, 4 and 5, a check valve assembly 28. The check valve assembly 28 comprises a housing 238 having at one end a threaded opening 240 in which is screwed an elbow fitting 242 by means of which the conductor 30 is connected at one end to the housing 238. The housing 238 has at its other end a threaded opening 244 into which is screwed a threaded nipple 246. The nipple 246 contains a threaded opening 247 into which is screwed an elbow fitting 248 by means of which the conductor 26 is connected to the upper end of the housing 238. Within the housing there is a chamber 250 at the bottom of which there is a central opening 256, and a diametrically disposed slot 254. At the top of the chamber there is a shoulder 260, on which there is supported a washer 262 containing a central opening 266. The washer is comprised of a resilient material and is held engaged with the shoulder 260 by the threaded end of the nipple 246. A flat light weight disk 268 which is of larger diameter than the opening 256,

but smaller in diameter than the length of the slot 254 is disposed in the chamber at the bottom so as to be free to move from the bottom upwardly therein against the washer 262. Under normal operating conditions, the sensing pressure flows through the check valve around the disk 268, which rests on the bottom and into the sensing tube. If an abnormal back pressure develops causing the liquid in the container to rise into and through the sensing tube, the disk 268 will be raised against the washer 262, closing the opening 266 so that there can be no back flow of a liquid through the check valve into the valve block.

The flow diaphragm for the control circuit described above is shown diagramatically in FIG. 6 and referring thereto the high-pressure conductor is indicated at 12, the sensing pressure conductor at 14 and the blowdown pressure conductor at 16. The trip valves are shown at 61 and 107 respectively.

Referring to FIG. 6 high-pressure air is delivered directly through the conductor 12 to the trip valve 107, valve unit 36, nozzle 122 and valve unit 61 and indirectly through the valve unit 36 to the cylinder 20 which opens the filling valve in the filling nozzle. Tripping the valve unit 61 will initiate the filling operation provided a container is in place for filling by supplying pilot pressure through the pilot passage 60 to the valve unit 36. When the filling operation is completed and the liquid in the container rises to the end of the sensing tube the diaphragm 116 which moves the valve element 120 carried thereby closer to the nozzle 122 increases the pressure in the pressure chamber 124, and such increased pressure operates to move the valve element away from the nozzle 148, and, thus, exhausts the pressure in the pilot passage 60. Exhausting pressure from the chamber 42 permits the valve element 46 in the valve unit 36 to move from right to left to engage the head 48 with its seat and hence to block flow of pressure to the cylinder 20. The piston in the cylinder 20 is spring returned so as to retract the rod 22 and the retraction of the rod 22 allows the filling valve in the filling nozzle to close since it is also spring biased to its closed position.

in order to keep the end of the sensing tube clean and sensitive to the filling pressure, blowdown pressure is periodically applied to the sensing tube. This is achieved by tripping the valve unit 107 which delivers high pressure through a pilot passage 104 to the chamber 97. Delivery of high pressure to the chamber 97 shifts the valve element 92 therein before it actuates the valve assembly 180, so that communication between the intermediate chamber 94 and the passage 108 is blocked before the blowdown pressure is admitted to the chamber 95. The blowdown pressure is of short duration and to allow the valve element 94 to return to its sensing position, the piston 204 is provided with a small opening 270 through which the pilot pressure is allowed to bleed. The spring 210 returns the piston to the right end of the cylinder, withdrawing the piston rod 206, and this in turn allows the actuator 222 to be moved away from the ball valve 224 by the spring 230, thereby cutting off the blowdown pressure. The

valve element 92 is returned to its sensing position by I the spring 87. A vent passage 272 is provided in the valve part 212 (FIG. 3) to permit the pressure to escape to the atmosphere.

In the diagram, the parts denoted s represent a nocontainer, no-fill device which comprises a valve which is held in an open position so as to exhaust the pilot passage 60 so long as there is no container in position for filling, thereby preventing the trip valve 61 from initiating a filling operation. Also in this figure the sensing tube34 is shown dotted within the filling nozzle which is represented at N.

l claim:

1. in an apparatus for filling containers with liquid of the kind wherein there is a control circuit to which air pressure is supplied including means operable by said air pressure to initiate the filling operation and a sensing tube through which sensing air flows during the filling operation for stopping operation when the liquid reaches the end of the tube; first conductor means for supplying low pressure sensing air, second conductor means for supplying higher pressure blow-down air, a valve assembly comprising first and second valve elements, said first valve element being interposed in the first conductor means for supplying low pressure air to the sensing tube and said second valve element being interposed in the second conductor means for supplying higher pressure air to the first valve element, said first and second valve elements having open and closed positions such that said first valve element in its open position permits low pressure air to flow through it to the sensing tube and blocks flow through it to the second valve element and in its closed position prevents the higher pressure air from flowing through it into the low pressure first conductor means and permits high pressure air to flow through it to the sensing tube, first and second spring means normally holding respectively, the first and second valve elements respectively open and closed, said first spring means being less resistant to displacement than said second spring means, and means for supplying air pressure simultaneously to the first and second valve elements to effect displacement thereof, respectively, to their closed and open po sitions.

2. in an apparatus for filling containers with liquid of the kind wherein there is a control circuit to which air pressure is supplied including means operable by said air pressure to initiate the filling operation and a sensing tube through which sensing air flows during the filling operation for stopping operation when the liquid reaches the end of the tube; first conductor means for supplying low pressure sensing air, second conductor means for supplying higher pressure blow-down air, a valve assembly comprising first and second valve chambers, said first valve chamber having ports at its ends and an intermediate port, a first valve element movable therein to alternately connect the port at one end with the intermediate port and the port at the other end with the intermediate port, means connecting the port at the one end with the conductor means for supplying low pressure air, means connecting the intermediate port to the sensing tube, said second valve chamber containing ports, means connecting one of the ports of the second valve chamber to conductor means for supplying higher pressure air and another port of the second valve chamber to the port at the other end of the first valve chamber, a second valve element in said second chamber operable in one position to connect certain ports to each other and in the other position to disconnect said certain ports, spring means holding the valve elements in the first and second chambers, respectively, open and closed, and pressure-operable means associated with each of the valve elements responsive to a common pressure to close and open the valve elements respectively, said spring means for the first valve element being less resistant to displacement than the spring means for the second valve element such that the first valve element is closed before the second is open.

3. In a filling machine, a filling head including a nozzle and filling valve for controlling flow of material from the nozzle, means supporting the filling head in a predetermined position for presentation of a receptacle to the nozzle for filling, pneumatically operable means connected to the filling valve for opening and closing said filling valve, a control circuit, means for supplying pressure to said control circuit, first valve means in the control circuit for directing pressure therein to said pneumatically operable means to open said filling valve, a valve assembly in the control circuit including first and second valve elements, a sensing tube connected at one end to the valve assembly, means supporting the other end of the sensing tube adjacent the nozzle, first and second conductors connected to the valve assembly for delivering sensing air and blowdown air thereto, said first and second valve elements having first open and closed positions which, respectively, permit sensing air to flow from the first conductor to the sensing tube and block flow of blow-down pressure from the second conductor to the sensing tube and second, blow-down, closed and opened positions, respectively, which block flow of sensing pressure from the first conductor to the sensing tube and permit flow of blow down pressure from the second conductor to the sensing tube, means yieldingly supporting said valve elements at said first position during filling so that sensing air flows continuously from the sensing tube, means connected to said first conductor responsive to back pressure developed therein by blocking of the sensing tube to disable said first valve means and second valve means in the circuit for directing pressure in the circuit simultaneously to said valve elements when the filling valve is closed to move them to said second position, said means yieldably supporting the valve elements differentially resisting displacement of the valve elements from said first position such that displacement of the first valve element to its closed position precedes displacement of the second valve element to its open position.

4. Apparatus according to claim 3, wherein said means yieldably supporting the valve elements in said first position are, respectively, first and second springs and wherein the second spring is more resistant to displacement than the first spring.

5. Apparatus according to claim 4, wherein said second valve means for directing pressure in the circuit to said valve elements delivers a pulse of pressure thereto and there is a vent for exhausting said pulse of pressure delivered to said valve elements so that said first and second springs return, respectively, said first and second valve elements to their first position.

6. Apparatus according to claim 3, comprising a check valve interposed between the valve assembly and the one end of the sensing tube, said check valve containing a part normally held in an open position by the flow of sensing air through the check valve to the sensing tube and being movable to a closed position by flow of material therethrough in the opposite direction.

7. Apparatus according to claim 3, comprising a conductor connecting the one end of the sensing tube to the valve assembly, a check valve comprising a valve chamber interposed in said conductor, said chamber having vertically spaced upper and lower walls containing ports, and a light-weight disc situated in the chamber between the ports, said disc when engaged with the upper wall covering the port therein and when engaged with the lower wall permitting sensing air entering the upper port to flow around it through the lower port.

8. Apparatus according to claim 3, wherein the means responsive to said back pressure comprises a flexible diaphragm, means supporting said flexible diaphragm with one side exposed to the pressure in said first conductor so that the back pressure developed therein will effect displacement of the diaphragm, means yieldingly engaged with the diaphragm opposing such displacement and means for adjusting the resistance of said yieldable means to displacement.

9. Apparatus according to claim 8, wherein the diaphragm is supported at its peripheral edge in a horizontal position with its upper face exposed to said back pressure comprising a part at the center of the diaphragm which limits upward displacement of the diaphragm to a plane defined by its peripheral edge, and wherein said yieldable means yieldingly holds the diaphragm with said part at said limiting position.

10. Apparatus according to claim 8, wherein the flexible diaphragm is of the roll-type supported at its edge for movement perpendicular to its face and wherein said yieldable means comprises a coiled spring and there is means adjustably supporting the spring with one end engaged with the diaphragm.

11. Apparatus according to claim 10, comprising means at the side of the diaphragm exposed to the back pressure limiting displacement in opposition to the back pressure to the plane containing its peripherally supported edge.

12. Apparatus according to claim 3, wherein the means responsive to back pressure is a flexible diaphragm comprising a pressure chamber in said control circuit, a restrictor connecting the pressure chamber to the pressure in the control circuit, a vent in the pressure chamber through which the pressure in the pressure chamber vents at a predetermined rate such as to maintain the pressure therein at a pressure lower than the pressure in the control circuit, means supported by said flexible diaphragm for movement by displacement of the diaphragm to block the air venting from the pressure chamber, an exhaust port in the control circuit, an exhaust valve, a pair of spaced diaphragms supporting said exhaust valve for movement perpendicularly to their centers relative to said exhaust port, a spring engaged with said exhaust valve holding it against said exhaust port, and means subjecting the confronting sides of said spaced diaphragms to the pressure in said pressure chamber, said spaced diaphragms being of different effective area and the diaphragm more remote from the exhaust port being of larger effective area than the other.

13. Apparatus according to claim 3, comprising a trip valve in the control circuit for directing a pulse of air pressure to said first valve means to move it to a position to direct flow of pressure in the control circuit through it to said pneumatically operable means, means embodied in said first valve means for applying holding pressure to said first valve means to hold it open, and wherein the means for disabling said first valve means includes a vent for venting said holding pressure.

14. Apparatus according to claim 13, comprising a normally closed vent valve in the control circuit for disabling the trip valve, and wherein the means responsive to back pressure opens said normally closed vent valve.

15. Apparatus according to claim 14, wherein said valve assembly in the blow-down position disables said trip valve. 

1. In an apparatus for filling containers with liquid of the kind wherein there is a control circuit to which air pressure is supplied including means operable by said air pressure to initiate the filling operation and a sensing tube through which sensing air flows during the filling operation for stopping operation when the liquid reaches the end of the tube; first conductor means for supplying low pressure sensing air, second conductor means for supplying higher pressure blow-down air, a valve assembly comprising first and second valve elements, said first valve element being interposed in the first conductor means for supplying low pressure air to the sensing tube and said second valve element being interposed in the second conductor means for supplying higher pressure air to the first valve element, said first and second valve elements having open and closed positions such that said first valve element in its open position permits low pressure air to flow through it to the sensing tube and blocks flow through it to the second valve element and in its closed position prevents the higher pressure air from flowing through it into the low pressure first conductor means and permits high pressure air to flow through it to the sensing tube, first and second spring means normally holding respectively, the first and second valve elements respectively open and closed, said first spring means being less resistant to displacement than said second spring means, and means for supplying air pressure simultaneously to the first and second valve elements to effect displacement thereof, respectively, to their closed and open positions.
 2. In an apparatus for filling containers with liquid of the kind wherein there is a control circuit to which air pressure is supplied including means operable by said air pressure to initiate the filling operation and a sensing tube through which sensing air flows during the filling operation for stopping operation when the liquid reaches the end of the tube; first conductor means for supplying low pressure sensing air, second conductor means for supplying higher pressure blow-down air, a valve assembly comprising first and second valve chambers, said first valve chamber having ports at its ends and an intermediate Port, a first valve element movable therein to alternately connect the port at one end with the intermediate port and the port at the other end with the intermediate port, means connecting the port at the one end with the conductor means for supplying low pressure air, means connecting the intermediate port to the sensing tube, said second valve chamber containing ports, means connecting one of the ports of the second valve chamber to conductor means for supplying higher pressure air and another port of the second valve chamber to the port at the other end of the first valve chamber, a second valve element in said second chamber operable in one position to connect certain ports to each other and in the other position to disconnect said certain ports, spring means holding the valve elements in the first and second chambers, respectively, open and closed, and pressure-operable means associated with each of the valve elements responsive to a common pressure to close and open the valve elements respectively, said spring means for the first valve element being less resistant to displacement than the spring means for the second valve element such that the first valve element is closed before the second is open.
 3. In a filling machine, a filling head including a nozzle and filling valve for controlling flow of material from the nozzle, means supporting the filling head in a predetermined position for presentation of a receptacle to the nozzle for filling, pneumatically operable means connected to the filling valve for opening and closing said filling valve, a control circuit, means for supplying pressure to said control circuit, first valve means in the control circuit for directing pressure therein to said pneumatically operable means to open said filling valve, a valve assembly in the control circuit including first and second valve elements, a sensing tube connected at one end to the valve assembly, means supporting the other end of the sensing tube adjacent the nozzle, first and second conductors connected to the valve assembly for delivering sensing air and blow-down air thereto, said first and second valve elements having first open and closed positions which, respectively, permit sensing air to flow from the first conductor to the sensing tube and block flow of blow-down pressure from the second conductor to the sensing tube and second, blow-down, closed and opened positions, respectively, which block flow of sensing pressure from the first conductor to the sensing tube and permit flow of blow-down pressure from the second conductor to the sensing tube, means yieldingly supporting said valve elements at said first position during filling so that sensing air flows continuously from the sensing tube, means connected to said first conductor responsive to back pressure developed therein by blocking of the sensing tube to disable said first valve means and second valve means in the circuit for directing pressure in the circuit simultaneously to said valve elements when the filling valve is closed to move them to said second position, said means yieldably supporting the valve elements differentially resisting displacement of the valve elements from said first position such that displacement of the first valve element to its closed position precedes displacement of the second valve element to its open position.
 4. Apparatus according to claim 3, wherein said means yieldably supporting the valve elements in said first position are, respectively, first and second springs and wherein the second spring is more resistant to displacement than the first spring.
 5. Apparatus according to claim 4, wherein said second valve means for directing pressure in the circuit to said valve elements delivers a pulse of pressure thereto and there is a vent for exhausting said pulse of pressure delivered to said valve elements so that said first and second springs return, respectively, said first and second valve elements to their first position.
 6. Apparatus according to claim 3, comprising a cheCk valve interposed between the valve assembly and the one end of the sensing tube, said check valve containing a part normally held in an open position by the flow of sensing air through the check valve to the sensing tube and being movable to a closed position by flow of material therethrough in the opposite direction.
 7. Apparatus according to claim 3, comprising a conductor connecting the one end of the sensing tube to the valve assembly, a check valve comprising a valve chamber interposed in said conductor, said chamber having vertically spaced upper and lower walls containing ports, and a light-weight disc situated in the chamber between the ports, said disc when engaged with the upper wall covering the port therein and when engaged with the lower wall permitting sensing air entering the upper port to flow around it through the lower port.
 8. Apparatus according to claim 3, wherein the means responsive to said back pressure comprises a flexible diaphragm, means supporting said flexible diaphragm with one side exposed to the pressure in said first conductor so that the back pressure developed therein will effect displacement of the diaphragm, means yieldingly engaged with the diaphragm opposing such displacement and means for adjusting the resistance of said yieldable means to displacement.
 9. Apparatus according to claim 8, wherein the diaphragm is supported at its peripheral edge in a horizontal position with its upper face exposed to said back pressure comprising a part at the center of the diaphragm which limits upward displacement of the diaphragm to a plane defined by its peripheral edge, and wherein said yieldable means yieldingly holds the diaphragm with said part at said limiting position.
 10. Apparatus according to claim 8, wherein the flexible diaphragm is of the roll-type supported at its edge for movement perpendicular to its face and wherein said yieldable means comprises a coiled spring and there is means adjustably supporting the spring with one end engaged with the diaphragm.
 11. Apparatus according to claim 10, comprising means at the side of the diaphragm exposed to the back pressure limiting displacement in opposition to the back pressure to the plane containing its peripherally supported edge.
 12. Apparatus according to claim 3, wherein the means responsive to back pressure is a flexible diaphragm comprising a pressure chamber in said control circuit, a restrictor connecting the pressure chamber to the pressure in the control circuit, a vent in the pressure chamber through which the pressure in the pressure chamber vents at a predetermined rate such as to maintain the pressure therein at a pressure lower than the pressure in the control circuit, means supported by said flexible diaphragm for movement by displacement of the diaphragm to block the air venting from the pressure chamber, an exhaust port in the control circuit, an exhaust valve, a pair of spaced diaphragms supporting said exhaust valve for movement perpendicularly to their centers relative to said exhaust port, a spring engaged with said exhaust valve holding it against said exhaust port, and means subjecting the confronting sides of said spaced diaphragms to the pressure in said pressure chamber, said spaced diaphragms being of different effective area and the diaphragm more remote from the exhaust port being of larger effective area than the other.
 13. Apparatus according to claim 3, comprising a trip valve in the control circuit for directing a pulse of air pressure to said first valve means to move it to a position to direct flow of pressure in the control circuit through it to said pneumatically operable means, means embodied in said first valve means for applying holding pressure to said first valve means to hold it open, and wherein the means for disabling said first valve means includes a vent for venting said holding pressure.
 14. Apparatus according to claim 13, comprising a normally closed vent valve in the control circuit for disabling the trip valve, And wherein the means responsive to back pressure opens said normally closed vent valve.
 15. Apparatus according to claim 14, wherein said valve assembly in the blow-down position disables said trip valve. 